Acidified diatomaceous earth filter aids



Patented Nov. 10, 1942 \JUL I bl] 2,301,623 ACIDIFIED DIATOMgCEOUS EARTHFILTER IDS Milo A. Harrison, Hermosa Beach, Calif., assignor to TheDicalite Company, Los Angeles, Calif., a corporation of Nevada NoDrawing. Application November 12, 1941, Serial No. 418,850

4 Claims.

The instant application is a division of my copending applicationentitled Acidified diatomaceous earth filter-aids, filed April 9, 1938,under Serial No. 201,188.

The invention relates to the treatment of various oils, fats and aqueousliquids with diatomaceous earth filter-aids for the clarificationthereof, and to the production of a filter-aid containing free acidwhich may advantageously be substituted for the conventional filter-aidsin certain instances.

An object of the invention is to prevent reversion or darkening of thecolor of certain liquids +following their clarification by the use ofdiatomaceous earth filter-aids.

An object of the invention is to prevent a change in the pH value ofcertain liquids which may otherwise follow their clarification by theuse of filter-aids.

An object of the invention is to promote and maintain the suspension incertain liquids of diatomaceous earth powders used as fillers or bodyingagents.

It is common practice to filter various liquids with the addition ofsmall quantities of finely comminuted diatomaceous earth, for thepurpose of removing water cloud, mucilaginous substances, finely dividedsolid particles and other suspensions which are not removable byfiltration without the addition of the filter-aid. In some cases theclarification only of the liquid is accomplished, in others theclarification is accompanied by partial decolorization, which may be dueto the removal of dark colored suspensoids or to actual adsorption ofcoloring matters originally in solution.

Normally, the liquid thus clarified has a color stability at least equalto that of the original liquid, but to this rule there are importantexceptions. For instance, cocoanut oil which has been clarified with adiatomaceous earth filteraid tends to darken rather rapidly afterclarification, particularly as to the red constituent of the totalcolor. This effect is more pronounced with the use of calcined earthsthan when natural or uncalcined earths are used, and is still morepronounced when calcination has been offected with the use of a fluxingagent. The

-unbleached condition or partially or higher temperatures of calcinationalso appear to increase the tendency toward color reversion, as does thepresence of iron (such as the walls of tanks or tank cars) in contactwith the clarified oil.

I have discovered that by the addition to the filter-aid, or to the oilinto which the filter-aid is introduced, of a minute proportion of asuitable acid, the tendency of the earth to produce color reversion inthe clarified oil may completely be overcome and the color of the oilthereby stabilized. I have also discovered that this addition oftentends to increase the bleaching power of the earth or to impartbleaching power under conditions where it does not otherwise exist.

As examples of these phenomena I cite the following results taken from alarge number of tests directed to determine the extent of the tendencytoward color reversion exhibited by cocoanut oils clarified by the useof diatomaceous earth filteraids, and the dosages of acid necessary tocorrect this tendency. In making the tests of which the results arerecited in the following table, the oil used was the same throughout(crude expeller oil) but in the different groups was either in the fullybleached by treatment with a well known bleaching clay. Likewise, theearth used as a filter-aid was the same throughout as to its originalcharacter but, as noted in the left-hand column of the table, wasdifierently heat treated in different tests. Explaining this legend, thenatural earth was heated only to substantial dryness, the"semi-calcined" earth was heat treated to about 1200 Fahr., the calcinedearth was heat treated to about 1800 Fahr. without the use of a fluxingagent, and the processed" earth was heat treated at about 1800 Fahr.with the use of a fluxing agent (sodium silicate).

In each case the dosage of filter-aid is stated in percents of theweight of oil taken to be clarified, and the dosage of acid in percentsof the weight of filter-aid applied. Citric acid only was used in thisseries of tests. The clarification was performed in the usual manner, bymixing the oil with the filter-aid and filtering. The red constituent ofthe color, in Lovibond units, was determined in a 1" column, immediatelyafter clarification and after standing for one day and for three days ata temperature of 120 Fahr.

Red constituent Dosage Flltqrgd of fil- Dosage of acid condition turgidInitial 1 day 3 days No.

Per ccnl Per cent [3. ll. 3 0. 4 l 3. 6 4. l 4. 2 4. 2 4. 5 5. 3 3 5. 4(1.0 7. 5 4

3. l 3. 3 4. 0 5 3. i 5. 7 6.8 Ii 2. 3 3. 7 4. 3 7 2. 2 2. 2 2. 2 8 2. 32. 0 2. 0 9 2. 2 2. 2 2. 0 10 Bleached oil None Nonc, 1.0 1.0 1.3 11Natural do 0. 5 0.5 1. 0 12 l. 5 1. G 2. 7 13 l. 8 3. 3 5. 5 14 2. 5 5.8 (i. 5 l5 1. 7 3.8 4. 7 16 1. 5 1. 3 1.5 17 1. 3 1. l l. 2 18 calcinedM..." None l. 7 3. J 3. 7 19 D0. 1.0 1,2 0.8 1.0 20

In considering the above figures it should be remembered that thefiltering value of the filteraid increased progressively from natural,having the lowest flow rate, to processed, having the highest. Inpractice only the calcined and the processed earths give sufficientthroughput to be commercially useful in this connection and thereforethe better results as to color shown by the table as following the useof natural rather than processed earth are not actually realizable.

It should also be stated that while, for purposes of comparison, thesame earth was used throughout these tests, the results obtained are notpeculiar to this earth but are realized with several other earths fromdifferent sources which were experimented with on a less complete scale.

The figures show a slight tendency toward color reversion in the oilsthemselves, without the addition of filter-aid, this tendency beingleast in the case of the fully bleached oil (see tests 1, 5 and 11).

The use of either of the filter-aids without acid produces an initialbleach when applied to an unbleached oil (tests 1 to 4) but only thenatural earth produces this result when applied to bleached oil (tests11 and 12). The use of semicalcined, calcined or processed earth onbleached oil produces a progressive initial darkening of the color(tests 11, 13, 14 and 15).

The addition of A; of 1% of citric acid to the processed filter-aidproduces an initial bleach of the semibleached oil whereas this earthwithout acid gives an initial darkening (tests 5, 6 and 7) Larger dosesof acid do not materially increase the initial bleach (tests '7 to 10).The addition of increasing doses of acid, however, progressively reducesthe initial darkening due to the use of processed earth on bleached oil(tests 15 to 18).

The addition of of 1% of acid to the processed earth did not overcomethe tendency toward reversion of color in either semibleached orbleached oils (tests 7 and 16) but 1% of acid in the earth applied tothe semibleached oil and of 1% in the case of the bleached oilcompletely 0Vercame this tendency (tests 8 and 17).

Larger doses of acid had no further effect (tests 8 to 10 and tests 17and 18).

These results are wholly surprising and no explanation can be offered asto why the presence of these minute amounts of acid should stabilize thecolor of the oil nor, for that matter, as to why the filter-aidincreases the relatively slight natural tendency of the original oiltoward reversion.

The same effect, of color stabilization, is shown to a lesser degree inthe clarification of other fatty oils and fats. A few observations ofthis kind are recorded below, In these tests two samples of each oil orfat were filtered, one with a processed filter-aid without the additionof acid, the other with the addition of a quantity of citric acid equalto of 1% of the weight of the oil. The clarified samples were thenmaintained at a temperature of Fahr. for three days.

In the table below, the last three columns record the reading of the redconstituent of the color on A==the oil prior to clarification;

B alfter clarification without acid and after heating for three days;

C=after clarification with acid and after heating for three days.

The relatively small change from the A to the B column is believed tobe, at least in part, due to the fact that the original oils had allbeen alkali treated and thereby substantially stabilized. A sample ofcrude oitiea oil blackened when filtered without acid and suffered noappreciable color change when filtered with acid.

The beneficial effect of acidification of the earth is also shown in themanipulation of some aqueous liquids, such as whiskey, acid wines andfruit juices.

In the case of whiskey, and particularly after this liquid has beenstored in wood barrels, clarification is often required, and itsometimes occurs that the use of diatomaceous earth filteraids for thispurpose causes a serious darkening of the color. This darkening isobserved in the filtrate as received and is not properly colorreversion, in which a time element is involved.

As an example, a certain whiskey having originally pH 4.2 (Allisonpotentiometer) was raised to pH 4.5 by clarification with a processedearth of pH 7.5 (in 5% aqueous suspension) and the color was so darkenedas to render the liquor unmarketable. When 1% by weight of citric acidwas added to the earth, bringing its pH to 3.3, the clarified liquor hadits original pH of 4.2 and darkening of color was entirely avoided.

In the clarification of fruit juices and other aqueous liquidscontaining pectins, the use of a diatomaceous earth filter-aid tends, insome cases, to cause the formation of a cloudy precipitate in theclarified liquid after standing for some time. This tendency is entirelyavoided by uuulbll acidifying the filter-aid to such extent as sufficesto maintain in the clarified liquid the same pH value as that of theoriginal liquid, prior to the addition of the filter-aid,

In the above cases, and others of similar character, the pH of theacidified earth is not the governing factor, the criterion being toavoid disturbing the original pH value of the liquid to which thefilter-aid is applied. This is accomplished by adding to the earth, orto the liquid, such quantity of acid as to offset that withdrawn by thefilter-aid through adsorption or otherwise.

In other cases, however, the pH of the earth as used is the controllingfactor, as in its use as a filler or bodying agent is varnishes,lacquers, liquid polishes, rubber compounds, plastics and paperfurnishes. In such uses, suspension and dispersion of the earth in theliquid may be produced more rapidly and maintained more readily bybringing the earth to a pH value not exceeding that of the material inwhich it is to be incorporated, and preferably to exactly the pH valueof that material.

As such materials have, almost without exception, a pH lower than thatof an unacidified diatomaceous earth, the correction and control of thepH value of the earth is accomplished by the addition of carefullygraduated quantities of an acid compatible with the particular compoundin which the earth is to be used, this addition of acid being madeeither to the earth prior to its use or to the material in the conductof the compounding step.

It has also been noted that the addition of diatomaceous earth as abodying material to certain resins, or its use for filtering such resinsor their constituents or varnishes made from them, may lead to anappreciable discoloration of the liquid. Such depreciation of the colormay wholly be avoided by bringing the earth to a pH not exceeding thatof the material being treated or bodied, and not exceeding 7.0, by theaddition of small amounts of free acid, or by the addition of anequivalent quantity of acid to the material to be treated or beingtreated.

While all of the experimental results recorded above were obtained withthe use of citric acid, other acids may be substituted and the choice ofacids is limited mainly by the nature and the use of the liquid to beclarified or the substance to be bodied. For example, in connection withthe clarification of oils destined for soap or grease making, and inmost bodying operations, it is possible to substitute sulfuric,hydrochloric, phosphoric, acetic or oxalic acid, while for the treatmentof edible oils or potable liquids the choice is practically limited tothe commercially available fruit acids such as citric and tartaric,tartaric acid being the full equivalent of citric acid in thisconnection.

So far as I am aware, the method by which the acid is added to the earthis immaterial, so long as it is finely subdivided and intimatelydispersed throughout the mass of comminuted earth particles. In practiceI prefer to spray a liquid acid or solution into the suction of a fanblower carrying a stream of earth in suspension in an air stream. Afinely powdered solid may be introduced in the same manner, or bytumbling or stirring.

While it is convenient and in many ways desirable to introduce the acidinto the liquid to be clarified in admixture with the earth, and in thecase of bodying agents to add the required quantity of acid to the earthprior to its use, the same results may in most cases be obtained byadding the acid to the liquid to be clarified or the substance to bebodied prior to or during the step of clarifying or compounding, It isnot known, nor is it believed, that the acid produces any change in theearth itself, and the invention is believed to lie in the simultaneouspresence, in the liquid undergoing treatment, of the diatomaceous earthbodying agent or filter-aid and the quantity of acid required to offsetundesired effects of the earth on the liquid.

In some cases the acid may even be added to the clarified liquid afterthe filter-aid has been removed and a substantial part of the desiredeffect thereby realized. An example is given in the followingcomparative tests in which the readings in the three columns are of thered component of the color when freshly filtered (initial), afterstanding one day and after standing ten days. The yellow component ofthe color was constant at 35 in all cases. The material tested was thecrude cocoanut oil used in preceding tests, the filter-aid was processedand citric acid was used in tests 23 and 34.

Initial lday 10 days 2i. Crude oil filtered through paper, no

filter-aid used 2. 3 3. 2 4. 3 22. Same oil filtered with 5% filter-aid,

Comparing the results from test 22 with those of test 21 it will be seenthat the use of the unacidified filter-aid depreciated the initial colorand also led to a greater depreciation of color on standing. Test 23, inwhich the acid was added to the oil along with the earth, shows aninitial color substantially that of the oil to which no earth had beenadded and materially less darkening of color on standing. The acid notonly corrected the depreciation of color caused by the earth to which noacid had been added but also reduced the natural tendency of the oil todarken on standing. Test 24, in which the acid was added to the filteredoil after removal of the filter-aid, shows an initial colorsubstantially that realized in test 22 and thus does not indicatecorrection of the original depreciation, but the color after standingfor ten days is better than that of the crude oil, showing that thetendency of the earth to cause subsequent darkening is corrected (inthis case) by the addition of the acid to the filtered oil.

I claim as my invention:

1. In the clarification of an alcoholic beverage the color of which isdarkened by contact with diatomaceous earth, the steps of adding to saidbeverage a diatomaceous earth filter-aid and a quantity of a free acidonly sufficient to offset said darkening efiect, and thereafter removingfrom said beverage said filter-aid and substances entrained therein.

2. The method of clarifying an alcoholic beverage the color of which isdarkened by contact with diatomaceous earth which comprises: mixing adiatomaceous earth filter-aid with said beverage; filtering saidfilter-aid from said beverage,

HUUl l and adding to the filtered beverage a quantity of free acid onlysuflicient to overcome the darkening effect produced by said admixedearth.

3. In the purification of alcoholic beverages the color of which isdarkened by contact with diatomaceous earth, the step of adding to saidbeverage a quantity of a diatomaceous earth filter-aid sufilcient forthe clarification of said beverage by filtration, together with aquantity of a fruit acid approximately one percent of the weight of saidadded filter-aid.

4. A method substantially as and for the purpose set forth in claim 1,in which said free acid is citric acid.

MILO A. HARRISON.

